1. Field of the Invention
This invention relates to a digitizing method and, more particularly, to a digitizing method in which tracing velocity at the time of digitizing is output as velocity data along with model profile data.
2. Description of Related
A method of creating NC data for performing machining in accordance with the profile of a model is available and includes tracing the surface of the model with a stylus by means of tracer control, digitizing the model surface profile by accepting stylus position data at a predetermined period T, and creating the NC data using the digitized data.
FIGS. 5(a) and 5(b) are explanatory view in which profile data indicative of the surface of a model MDL is digitized by two-way surface tracing. A stylus STL is moved in the direction of the X axis at a predetermined tracing velocity and up and down along the model MDL in the direction of the Z axis, and stylus three-dimensional position data (coordinates) Xi, Yi, Zi and displacement data .epsilon.x, .epsilon.y, .epsilon.z are accepted and stored at predetermined times or whenever predetermined conditions are satisfied. When the boundary of a tracing region TRR is reached, a predetermined amount of pick-feed is performed along the Y axis. Thereafter, the position and displacement of the stylus STL are monitored while surface tracing is performed in the same manner, the resulting position data and displacement data is accepted, the surface profile of the model MDL is digitized, and NC data is subsequently created using the digitized data.
In general, when digitizing is carried out by such tracing, stylus center-position data and displacement data is read in but velocity information is not. When the NC data is created, feed rate is set by an F code using an MDI unit (manual data input unit) or the like.
However, if the set F code (feed rate) is greater than the machining capability of the machine tool, tool breakage can result. Conversely, if the F code is less than the machining capability of the machine tool, too much machining time is required.
Consequently, when performing machining by NC data created using digitized data, it is required conventionally that the operator manipulate an override switch or the like to vary the machining velocity, which is based on the F code, over a range of, say, 0-120%, or to revise the machining velocity to an appropriate value.